Chapter 6 Uldp Function Configuration; Uldp Function Introduction - Edge-Core ES4624-SFP Basic Management Manual

Chapter 6 ULDP Function Configuration

6.1 ULDP Function Introduction

Unidirectional link is a common error state of link in networks, especially in fiber links.
Unidirectional link means that only one port of the link can receive messages from the
other port, while the latter one can not receive messages from the former one. Since the
physical layer of the link is connected and works normal, via the checking mechanism of
the physical layer, communication problems between the devices can not be found. As
shown in Graph, the problem in fiber connection can not be found through mechanisms
in physical layer like automatic negotiation.
This kind of problem often appears in the following situations: GBIC (Giga Bitrate
Interface Converter) or interfaces have problems, software problems; hardware becomes
unavailable or operates abnormally. Unidirectional link will cause a series of problems,
such as spinning tree topological loop, broadcast black hole.
ULDP (Unidirectional Link Detection Protocol) can help avoid disasters that could
happen in the situations mentioned above. In a switch connected via fibers or copper
Ethernet line (like ultra five-kind twisted pair), ULDP can monitor the link state of physical
links. Whenever a unidirectional link is discovered, it will send warnings to users and can
Fig 6-1 Fiber Cross Connection
Fig 6-2 One End of Each Fiber Not Connected
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